Although squeeze bottle types sprayers have been used for many years, such sprayers were largely replaced for a long period of time by pressurized can dispensing systems. A major advantage to the use of pressurized cans is the nearly instantaneous spraying which occurs upon actuation. However, there has been an increasing concern over the harmful effects on the atmosphere of the propelling gases, such as fluorocarbons, which are used in such pressurized cans. In addition, pressurized can dispensing systems are relatively expensive to manufacture. Accordingly, squeeze bottle type sprayers and manual pump sprayers have become more prevalent in recent years.
Products which can be dispensed in the form of a spray can be easily atomizable liquids, such as water based materials, or viscous materials which are more difficult to atomize such as oil based materials. In the case of a pressurized can there is sufficient force available for mechanical means to break up liquid droplets into a fine spray. However, in squeeze bottle type sprayers the force required to break up droplets must be supplied manually, that is by squeezing the bottle. Therefore, it is much more difficult to achieve a high degree of atomization with such bottles.
Squeeze bottle type sprayers typically utilize a dip tube for directing liquid to a mixing chamber. Upon squeezing the bottle, air located above the liquid level is forced under pressure through a passage toward the mixing chamber where it impinges on a stream of the liquid in an effort to break up the liquid into droplets. The liquid is dispersed in a spray pattern through an orifice in the mixing chamber.
One major drawback to the use of dip tubes in conventional venturi squeeze bottles is that there is a delay in the dispensing of spray from the orifice upon squeezing the bottle. This delay is caused by the time which it takes for liquid to travel up the length of the dip tube upon squeezing the bottle. The delays become more prominent as product is used up and the level of fluid in the bottle drops. When the fluid level drops close to the container bottom, as much as 75% of a full "squeeze" may be required to raise the liquid up the length of the dip tube. Such delays are not encountered when using pressurized cans. It would therefore be advantageous to eliminate or abate the above described lag time in squeeze bottle type sprayers so as to emulate the nearly instantaneous spraying which occurs when using pressurized cans.
Another drawback to spray dispensing devices is that it has not been possible to effectively vary the liquid to air ratio of the dispensed spray. For example, U.S. Pat. No. 4,401,270 describes a typical squeeze bottle type sprayer which can dispense liquid in only two possible spray patterns, either a pure liquid stream or an air-liquid mixture having a fixed liquid/air ratio. It would be advantageous to provide a sprayer device which is capable of dispensing product such that the liquid to air ratio can be varied to provide either a wet spray or a dry spray, as desired.